Attempts will be made to demonstrate active transport of K ion vesicles reconstituted from purified (sodium plus potassium)-activated adenosinetriphosphatase (NaK ATPase). Potassium transport will be compared with Na ion transport, which has already been studied in some detail, and stoichiometries will be determined. Antibodies against the intact pure Nak ATPase, the catalytic subunit and the glycoprotein will be prepared, and their effects on Na ion and K ion transport will be studied. The sequence of amino acids around the active site of the NaK ATPase will be determined. To be this, enzyme will be phosphorylated by incubating with Na ion, Mg ions, and (P32) ATP, digesting with pepsin, isolating the (P32) peptide by paper electrophoresis, reducing the peptide with Na (H3) borohydride, which will convert the phosphorylated residue to a(H3) homoserine residue, which is stable, and further puridication of the tritium-labelled peptide to homogeneity. Sequencing of the peptide can then be carried out. We will also compare the chemical properties of two NaK ATPases purified in our laboratory, that from the rectal gland of Squalus acanthias and that from the electric organ of Electrophorus electricus. The glycoprotein and the catalytic subunit will be isolated in milligram quantities by methods already worked out in the laboratory. The following studies will be done: amino acid analysis, N-terminal amino acid analysis, carbonhydrate analysis, measurement of the stoichiometry of the two subunits. Comparisons of phospholipid compositions, ouabain-binding capacity, and phosphorylation will also be carried out with the native enzymes.